The invention relates to a method of manufacturing an optical lens system including a housing, a first lens element having a first optical axis, and a second lens element having a second optical axis. According to the method, the lens elements, before being secured to the housing, are aligned relative to each other such that the optical axes of the lens elements coincide.
The invention further relates to an optical scanning device for scanning an information track of an optically scannable information carrier. The scanning device includes a radiation source, an optical lens system having an optical axis for focusing a radiation beam supplied, in operation, by the radiation source into a scanning spot on the information carrier, and a first actuator for displacing the lens system in a direction parallel to the optical axis. The lens system includes a first lens element, a second lens element and a second actuator for displacing the first lens element and the second lens element relative to each other.
The invention also relates to an optical player including a table which can be rotated about an axis of rotation, an optical scanning device for scanning an information track of an optically scannable information carrier which can be arranged on the table, and a displacement device which displaces the scanning device, in operation, relative to the axis of rotation, predominantly in a radial direction.
An optical lens system manufactured in accordance with a method of the type mentioned in the opening paragraph, as well as an optical scanning device and an optical player of the types mentioned in the opening paragraphs are known from U.S. Pat. No. 5,712,842. The known optical lens system used in the known optical scanning device includes an objective lens and a relatively small, so-called solid immersion lens, which is arranged between the objective lens and the information carrier to be scanned. By using the solid immersion lens, the known lens system has a relatively large numerical aperture, so that a relatively small scanning spot on the information carrier to be scanned is obtained. As a result, the known scanning device can suitably be used to scan information carriers having relatively small elementary information characteristics, i.e. information carriers having a relatively high information density, such as a high-density CD. Using the first actuator of the known scanning device, the lens system is displaced parallel to the optical axis, thus enabling the scanning spot to be focused on the information layer of the information carrier. Using the second actuator of the known scanning device, the solid immersion lens is displaced relative to the objective lens in a direction parallel to the optical axis, thus enabling a spherical aberration of the radiation beam in a transparent protective layer of the information carrier between the information layer and the scanning device to be corrected.
The objective lens of the known optical lens system is secured to the housing of the lens system in a fixed position, while the solid immersion lens is secured to the housing via a leaf spring. For a good optical operation of the lens system, the optical axes of the objective lens and the solid immersion lens must coincide as much as possible. To achieve this, in the course of the manufacture of the lens system, the objective lens and the solid immersion lens are aligned relative to each other, before being secured to the housing of the lens system, in such a manner that the optical axes of the objective lens and the solid immersion lens coincide as much as possible.
The above citations are hereby incorporated in whole by reference.